July 30, 2025
24 Cloud Cost Horror Stories Redditors Shared That’ll Keep You Up at Night
10 min read
What’s the most terrifying thing about the cloud? It’s not the uptime. It’s not even the security vulnerabilities. It’s the bill you didn’t see coming.
We asked folks across multiple Reddit communities to spill their worst cloud cost horror stories, the kind that CFOs still have nightmares about. There’s autoscaling gone wild, there’s rogue Lambdas and there's forgotten BigQuery jobs. The responses flooded in, and they did not disappoint!
Some of these are hilarious in hindsight, others are downright painful. All of them are real.
So grab your coffee (and whoever takes care of your budget), and settle in. These are 24 times the cloud said “thank you for your business”, and really meant it.
Let’s dig in right away.
The "set it and forgot it" nightmares
DDoS on a public S3 bucket racked up $450K in data transfer. Reserved Instances in the wrong region. Linux servers with Windows RIs. A triple threat.
Sometimes it’s not what you do, it’s what others do to you.
Left a debug-level log and c5.24xlarge running all weekend, bill jumped from $80 to $9,000.
When one missed shutdown became a budget-crushing oversight.
A Jenkins server with 1TB of memory left running for a weekend = an invoice that could buy the server outright.
Lesson learned: you’ve to treat the cloud like a hotel, not real estate.
Forgot to delete legacy CloudWatch log groups and accumulated 30TB over 8 years = $2K/month.
Cloud logs never forget. Just made a mental note.
Admin misconfigured Lambda and CloudWatch, created a runaway feedback loop. $100K in 12 hours. If that wasn’t enough, this redditor also shares another cloud cost horror story where a GPU-intensive automation left running over a holiday weekend = $450K bill.
When automation meets inattention, disaster strikes.
Lambda retry loop went unnoticed, cost jumped from $0.12 to $400/day.
Exponential retry = exponential regret.
Spun up a managed NAT Gateway.
Managed NAT Gateway: because why pay rent when you can pay AWS instead?
Estate’s infra was “governed,” “administered,” and “operated”, burned 7 figures monthly
Everyone was in charge, so no one really was.
Unbounded autoscaling and DDoS disasters
When systems scale too well for their own good.
Startup torched $120K in 72 hours due to uncapped autoscaling triggered by a DDoS.
So, the idea is no ceiling = sky-high costs.
Old EC2 auto-scaling logic + upgrade delays = infinite instance respawn.
One auto upgrade killed uptime. And the CFO’s weekend.
Mistakes that exploded costs instantly
Misconfigurations and overlooked options that turned routine tasks into financial facepalms.
Changed log level, exceeded budget by $10K...per region (18 regions).
A $180K mistake made in just one click.
Created public exportable certs for testing = $300 spent in 2 minutes.
When your personal project gives you an enterprise-level damage.
Junior engineer transferred billions of 10KB objects to Glacier Deep Archive. Got billed for unused PUTs.
Storage class migration gone horribly wrong.
S3 lifecycle rule moved billions of objects, resulting in a $100K one-time fee.
Yes, it saves in the long run, if you wait 20 years.
KMS encryption increased due to uncached requests + GuardDuty + other services = spicy invoice.
Even encryption can cost you your sanity. So, you better keep your ‘guards’ up.
Cloud portal rollout bug caused agents to re-download 300MB repeatedly
No cache, no checksum, no chill.
Wrong Redis SKU across 4 Azure accounts = $150K in ~5 days
Terraform doesn’t ask “Are you sure?”, your finance team will.
Security & access mismanagement
When access control fails, the costs spiral.
Disgruntled employee used valid credentials to spin up GPU spot instances = 10x bill.
Because your cloud bill shouldn’t depend on who’s mad this week. This is where a FinOps tool like Amnic saves the day.
Contractor used root keys with no expiration. Hacked. Thousands of instances spun up. $120K in one day.
Pro tip: delete root keys. Seriously.
Dev and Ops gone rogue
When engineers meant well, but the cloud didn’t care.
Dev created garbage collection Lambda that logged every file in S3. Logs of logs ballooned to $15K/day.
Logging hygiene is more than just tidy code.
Aggressive GuardDuty monitoring + backfill spark job = surprise sky-high bill.
Security’s expensive when it’s not communicated.
Devs managed their own infra for a year = $2M+ in waste found in 3 months.
Self-service is great and all, until the invoice hits.
BigQuery script ran on dev on Friday night. By Saturday: €1M bill.
Querying your way to bankruptcy, one weekend at a time.
GPU-hungry Euro-devs = half of AWS East Coast GPU burned
When the code wasn’t CPU-optimized, but the bill clearly was.
Lessons (Painfully) Learned
If these cloud cost horror stories hit a little too close to home, maybe it’s time to take Amnic for a spin. Because no one wants to start their day with a six-figure cloud bill for resources they didn’t even use.
Here’s how you can get started:
Request a demo and chat with our expert team.
Sign up for a free 30-day trial to see Amnic in action, without any commitments.
Explore our free FinOps resources to start managing your cloud spend smarter.
